1. Field of the Invention
The present invention relates to a method of compressing bell sounds using recorded sounds and voice memos (hereinafter, referred to ‘sounds’) in mobile terminals and, more particularly, to a method of compressing sounds in mobile terminals, which compresses pulse code modulation (PCM) code generated by sampling sounds, using Lempel Ziv Welch (LZW) compression technique by applying a differential method.
2. Description of the Related Art
Generally, mobile terminals use Musical Instrument Digital Interface (MIDI) or recorded bell sounds in order to inform users of phone calls. MIDI bell sounds have been developing from existing mono-poly sounds to poly-poly sounds, and the recorded bell sounds use recorded music or voice to satisfy personal taste. Also, mobile terminals store voices so as to store details of the calling during on the line or to leave a memo during call waiting.
Presently, a method of storing sounds including bell sounds and voice memos used in mobile terminals uses a method of storing sounds using Adaptive Differential Pulse Code Modulation (ADPCM) compression algorithm without using sounds coder/decoder (CODEC) for supporting high tone quality provided by mobile terminals. Such ADPCM compression algorithm can reduce a storage space by about half level, but it cannot resist a degradation of tone quality.
In the existing method of storing sounds, voices are stored by transforming data sampled into PCM using ADPCM. PCM algorithm has been disclosed in International Telecommunications Union-Telecommunication Standardization Sector (ITU-T) G.711 Recommendations and ADPCM algorithm has been disclosed in ITU-T G.721 Recommendations.
The sounds storage method using the existing ADPCM described above has been improved, but it still has problems in that memories are excessively consumed and original sounds cannot be restored as they are because the method uses compression technique causing damage of source data.